Common Rue Ruta graveolens Rue is an evergreen shrub with an upright, rounded form and cool, ferny blue-green foliage. Clusters of cup-shaped, four-petaled yellow flowers appear in summer. Care: Grow in moderately fertile, very well-drained soil. Thrives in hot, dry sites. Propagation: Root semi-ripe cuttings in summer. Problems: Phytophthora root rot.